Synergistic compositions

ABSTRACT

A method of controlling veterinary ectoparasites of mammals and birds of the sub-Orders Ixodoidea and Sarcoptiformes comprising the application of a parasiticidally effective, non-toxic amount of a pyrethroid of formula  (* CHEMICAL STRUCTURE *)  together with at least one parasiticidal organophosphoruscompound active against said ectoparasites.

This is a continuation of U.S. Ser. No. 07/796,707, filed Nov. 21, 1991,now abandoned, which is a continuation of U.S. Ser. No. 07/672,734,filed Mar. 21, 1991, now U.S. Pat. No. 5,096,895, which is acontinuation of Ser. No. 07/432,989, filed on Nov. 6, 1989, nowabandoned, which is a division of U.S. Ser. No. 06/575,486, filed Jan.31, 1984, now U.S. Pat. No. 4,897,386, which is a division of U.S. Ser.No. 06/391,455, filed Jun. 23, 1982, now abandoned, which is acontinuation of U.S. Ser. No. 05/863,738, filed Dec. 23, 1977, nowabandoned.

This invention relates to novel potentiating compositions, theirpreparation, formulations containing them, the preparation of suchformulations and to their use for the control of pests of the sub-OrdersIxodoidea and Sarcoptiformes.

Pyrethroids embraced by formula (I): ##STR2## are known from UK PatentNo. 1,413,491 to possess insecticidal activity, and are known from SouthAfrican Patent No. 3211/1975 to possess acaricidal activity.

Pests of the Class Insecta and of the Order Acarina are troublesome toman, animal and plants. They are vectors of disease, and economic lossesresult from their depredations on plants and animals. Control of suchpests over the years has come to depend strongly upon the use ofchemical pesticides which can be naturally occuring compounds orsynthetic organic chemicals.

Organophosphorus pesticides are used in both the agricultural andveterinary fields with varying degrees of success. Some of thesesubstances are common to both fields such as diazinon and malathionwhilst others have been solely employed in the agricultural field, forexample fenitrothion. In recent years resistance to organophosphoruscompounds has evolved in certain strains of Insects and Acarids both ofagricultural and veterinary importance and accordingly the need for new,effective insecticides and acaricides has arisen.

It is known from Japanese Patent Publication No. 058-237/1975, thatpotentiation of activity occurs between a pyrethroid of formula (I) andcertain organophosphorus compounds against Insects and certain Mites ofagricultural importance. Employing such potentiating compositions,renders the use of pyrethroids of formula (I) more economic. TheJapanese publication also suggests that the potentiation is due to theinteraction between the inhibition of the enzyme acetyl-cholinesteraseby the organophosphorus compound at the ganglionic junctions of thepest, which results in ganglionic nerve paralysis, and the disturbanceof axonal nerve transmittance through the cell membranes of the nerveaxons of the pest by the pyrethroid, which results in impaired axonalnerve transmission.

It has now been surprisingly found that there is potentiation between apyrethroid of formula (I) and certain organophosphorus compounds againstpests of veterinary importance which are resistant to conventionalorganophosphorus compounds and which belong to the sub-Orders Ixodoideaand Sarcoptiformes. It is believed that the potentiation is due to theinhibition by the organophosphorus compound of certain esterases whichdegrade pyrethroids. The various rates at which different groups ofarthropod pests, even within the same Order of classification metabolisea pyrethroid makes it difficult to predict potentiation in one group ofarthropod pests from a knowledge of potentiation in another group. Thisunpredictability is demonstrated by the absence of potentiation ofinsecticidal activity between a compound of formula (I) and anorganophosphorus compound in respect of Insects of veterinaryimportance. (See Tables 6 to 9 below).

The pyrethroid for use in the present invention is selected from theesters embraced by formula (I) defined above. Structural formula (I) isintended to encompass all the possible geometric and optical isomers.More particularly the acid moiety of the ester may be selected from the(+)-cis-isomer, the (+)-trans-isomer, the (±)-cis-isomer, the(±)-trans-isomer and the (±)-cis-trans-isomer; the stereochemistryreferring to that of the cyclopropane ring.

The preferred pyrethroid of this invention is3-phenoxybenzyl-(±)-cis,trans-2,2-dimethyl-3-(2,2-dichlorovinyl)cyclopropane-1-carboxylate(permethrin).

The activity of these esters against pests of the sub-Orders Ixodoideaand Sarcoptiformes is potentiated when used in combination with at leastone organophosphorus compound.

More particularly, the esters may be used in combination with phosphateand phosphorothioate compounds possessing intrinsic acaricidal activity.The organophosphorus compounds found to be effective are:

O,O-diethyl-O-(3-chloro-4-methyl-7-coumarinyl) phosphorothioate(coumaphos);

O,O-diethyl-O-(2,5-dichloro-4-bromophenyl) phosphorothioate(bromophos-Ethyl);

2,3-p-dioxanedithiol-S,S-bis, O,O-diethyl phosphorodithioate(dioxathion),

O,O-diethyl-O-(3,5,6-trichloro-2-pyridyl) phosphorothioate(chlorpyrifos);

O,O,0',0'-tetraethyl, S,S'-methylenediphosphorodithioate (ethion);

3-(Dimethoxyphosphinyloxy)-N-dimethyl-ciscrotonamide (dicrotophos);

cis-1-methyl-2-(1-phenylethoxycarbonyl)vinylphosphate (crotoxyphos);

O-ethyl-O-(quinol-8-yl)phenylphosphorothioate (oxinothiophos);

(S-{5,7-dichlorobenzoxazol-2-yl-methyl}-O,O-diethyl phosphorodithioate)(benoxaphos);

S-[{(4-chlorophenyl)-thio]methyl}-O,O-diethyl phosphorodithioate(carbophenothion);

S-{(1,3-dihydro-1,3-dioxo-2H-isoindol-2-yl)-methyl}O,O-dimethylphosphorodithioate(phosmet);

2-Chloro-1-(2,4-dichlorophenyl)vinyldiethylphosphate (chlorfenvinphos)

and a 1:1 weight by weight mixture of chlorofenvinphos and dioxathion.

Particularly high potentiation is achieved with combinations containingcoumaphos, chlorfenvinphos, diazinon, ethion and the mixture ofdioxathion and chlorfenvinphos.

The potentiating compositions of this invention are highly effectiveagainst strains of acarines which are susceptible to conventionalorganophosphorus acaricides as well as to those strains which areresistant to conventional organophosphorus acaricides such as Boophilusmicroplus (Can.) and B. decoloratus (Koch) and in addition those strainsresistant to pyrethroids. The compositions of this invention maytherefore be used to control acarine ectoparasites of animals,particularly those ticks of the genera Boophilus, Rhipicephalus,Amblyomma, Hyalomma, Ixodes, Haemaphysalis, Dermacentor, and Anocentor,and mites of veterinary importance for example the sheep scab mitePsoroptes ovis, and other ectoparasites of the sub-Orders Ixodoidea andSarcoptiformes. Such ectoparasites infest stock and domestic animals andfowls, depending upon the location of the host and the particularectoparasite. Common hosts are cattle, pigs, sheep, goats, horses,camels, chickens, dogs and cats.

The compositions of this invention may be used for protecting the hostagainst infestations of Ixodid and Sarcoptic pests by application of thecompositions themselves or in a diluted form in known fashion, as a dip,a spray, a dust, a paste, cream, gel, foam, shampoo or grease, apressure-pack, an impregnated article, or a pour-on formulation. Dipsare not applied per se, but the animals are immersed in a dipping bathcontaining the dip wash. Sprays may be applied by hand or by means of aspray race or arch or automatic treadle. Dusts may be distributed overthe animals by means of a powder gun by hand application from suitablecontainers or incorporated in perforated bags attached to trees orrubbing bars. Pastes, foams, creams, gels, shampoos and greases may beapplied manually or distributed over the surface of an inert materialagainst which animals rub and transfer the material to their skins.Pour-on formulations are dispensed as a unit of liquid of small volumeon to the backs of animals such that all or most of the liquid isretained on the animals.

The compositions may be presented either as formulations ready for useon the animals or as formulations requiring further dilution prior toapplication, but both types of formulations comprise a pyrethroid asdefined above in combination with at least one organophosphorus compoundas defined above in intimate admixture with one or more carriers ordiluents. The carriers may be gaseous or solid or liquid or comprisemixtures of such substances and may be selected from one or more of thefollowing: a solvent, an inert carrier, wetting, stabilising,emulsifying, thickening, dispersing and surface active agents.

Dusts may be prepared by intimate admixture of the chosen compound witha powdered solid inert carrier for example suitable clays, kaolin,talcs, powdered chalk, calcium carbonate, Fuller's Earth, gypsum,diatomaceous earths and vegetable carriers.

Sprays of a composition of this invention may comprise a solution in anorganic solvent (e.g. those listed below) or an emulsion in water (dipwash or spray wash) prepared in the field from an emulsifiableconcentrate (otherwise known as a water miscible oil) or a waterdispersible powder which may also be used for dipping purposes. Theconcentrate preferably comprises a mixture of the active ingredients,with or without an organic solvent and one or more emulsifiers. Solventsmay be selected from kerosene, ketones, alkanols, xylene, aromaticnaphtha, and other solvents known in the formulating art. Theconcentration of emulsifiers may be varied within wide limits and areconveniently non-ionic or a mixture of non-ionic and anionicsurfactants. The non-ionic surfactants will include polyoxyalkyleneethers of alkyl phenols, or of alcohols. The anionic compounds includesalts of alkylaryl sulphonic acids.

Dip washes may be prepared not only from emulsifiable concentrates butalso from wettable powders comprising a composition of this invention inintimate admixture with an inert carrier and one or more surface activeagents, and possibly a stabiliser and/or an antioxidant.

Greases may be prepared from vegetable oils, synthetic esters of fattyacids or wool fat together with an inert base such as soft paraffin. Acomposition of this invention is preferably distributed uniformlythrough the mixture in solution or suspension. Greases may also be madefrom emulsifiable concentrates by diluting them with an ointment base.

Pastes are also semi-solid preparations in which a composition of thisinvention may be present as an uniform dispersion in a suitable basesuch as soft or liquid paraffin or made on a non-greasy basis withglycerin, mucilage or a suitable soap. As greases and pastes are usuallyapplied without further dilution they should contain the appropriatepercentage of the composition required for treatment.

Aerosol sprays may be prepared as a simple solution of the activeingredients in the aerosol propellant and a co-solvent such ashalogenated alkanes and the solvents referred to above, respectively.Pour-on formulations may be made as a solution emulsion or suspension ofa composition of this invention in a liquid medium which is of aviscosity such as to minimize loss of the formulation by run off fromthe surface of the animals. The pour-on formulation may be applied by adrenching gun, syringe or ladle or any other method known in the art.

A composition of the present invention preferably contains (5-95%) of adefined pyrethroid for example one selected from structural formula (I)and between (5-95%) of an organophosphorus compound defined hereinabove.The concentration of a composition applied to the pests or to theirenvironment may be in the range of (0.0001-20%).

It will be appreciated from the foregoing that what we will claim maycomprise any novel feature described herein, principally and notexclusively, for example:

(a) A novel composition comprising an ester of formula (I) incombination with at least one organo-phosphorus compound;

(b) A pesticidal formulation comprising a composition as defined inparagraph (a) together with a carrier therefor;

(c) A method of producing such a formulation; and

(d) A method of controlling veterinary ectoparasites of the sub-OrdersIxodoidea and Sarcoptiformes comprising the application to theectoparasite or its environment, a composition or formulation as definedin paragraph (a) or (b).

The following Examples are provided by way of an illustration of thepresent invention and should not be construed as in any way constitutinga limitation thereof.

EXAMPLE 1

Engorged female ticks of the Biarra strain of Boophilus microplus areimmersed, in groups of 20 ticks per concentration, in a range ofdilutions of the organophosphorus compound in combination with3-phenoxybenzyl (±) cis,trans-2,2-dimethyl-3-(2,2-dichlorovinyl)cyclopropane-1-carboxylate(hereinafter referred to as Permethrin) at different ratios oforganophosphorus compound to Permethrin.

The composite wash is prepared immediately prior to the test by dilution(with water) of the two constituents. The constituents may be in theform of miscible oil or wettable powder formulations. The desired rangeof concentrations for the test is obtained by further dilution of thismaster solution or wash.

The ticks are removed from the wash after 10 minutes, dried, and stuckdorsal side down on doublesided adhesive tape. They remain in thisposition for 14 days when the numbers laying viable eggs are determined.From this data a regression line is plotted (concentration against %inhibition of egg-production) and the IR90 and IR99 values determined(Table 1).

IR90=concentration at which 90% inhibition of egg-production occurs.

IR99=concentration at which 99% inhibition of egg-production occurs.

The values so obtained for the composite wash are compared with similarvalues obtained for the constituents of the composite wash when usedalone. By reference to the equation for the harmonic mean, the factor ofpotentiation is determined (Table 2).

The equation for the harmonic mean is: ##EQU1##

The FOP figures for the IR99 values were calculated in the same way.

                                      TABLE 1                                     __________________________________________________________________________    IR90/99 Values for the Ixodicides alone and Compositions                      of these with Permethrin at various Ratios                                    PERMETHRIN                                                                             IXODICIDE                                                            COMPOSITE                                                                              ALONE  RATIO 1:1                                                                           RATIO 1:5                                                                            RATIO 5:1                                                                           RATIO 10:1                                                                           RATIO 20:1                          WITH     IR90                                                                              IR99                                                                             IR90                                                                             IR99                                                                             IR90                                                                             IR99                                                                              IR90                                                                             IR99                                                                             IR90                                                                             IR99                                                                              IR90                                                                             IR99                             __________________________________________________________________________    Coumaphos                                                                              1.0 -- 0.016                                                                            0.024                                                                            .0016                                                                            .0030                                                                             0.038                                                                            0.092                                         Composition A                                                                          0.75                                                                              2.6                                                                              0.011                                                                            0.017                                                                            .0031                                                                            .0053                                                                             0.060                                                                            0.15                                          Bromophos Ethyl                                                                        0.18                                                                              0.38                                                                             0.010                                                                            0.016                                                                            .0058                                                                            .0098                                                                             0.064                                                                            0.12                                          Diazinon 1.0 -- 0.095                                                                            0.21                                                                             .0030                                                                            .0056                                                                             0.017                                                                            0.038                                         Dioxathion                                                                             1.0 -- 0.016                                                                            0.038                                                                            .0028                                                                            0.023                                                                             0.044                                                                            0.060                                         Chlorpyrifos                                                                            0.085                                                                            0.24                                                                             0.008                                                                            0.014                                                                            .0046                                                                            .0062                                                                             0.020                                                                            0.024                                         Ethion   0.14                                                                              0.23                                                                             0.015                                                                            0.024                                                                            .0032                                                                            .0055                                                                             0.099                                                                            0.054                                         Dicrotophos                                                                            1.0 -- 0.063                                                                            0.15                                                                             .0080                                                                            0.016                                                                             0.044                                                                            0.094                                         Chlorfenvinphos                                                                        0.15                                                                              0.42                                                                             0.015                                                                            0.024                                                                            .0015                                                                            .0030                                                                             0.018                                                                            0.085                                                                            0.043                                                                            0.070                                                                             0.067                                                                            0.096                            __________________________________________________________________________     Composition A: A 1:1, weight by weight mixture of Chlorfenvinphos and         Dioxathion                                                                    Key: -- Ratio Ixodicide/Permethrin                                       

                                      TABLE 2                                     __________________________________________________________________________    Factors of Potentiation of composites of                                      certain Ixodicides and Permethrin                                             PERMETHRIN                                                                    COMPOSITE   RATIO 1:1                                                                            RATIO 1:5                                                                            RATIO 5:1                                                                             RATIO 10:1                                                                           RATIO 20:1                           WITH        IR90                                                                              IR99                                                                             IR90                                                                              IR99                                                                             IR90 IR99                                                                             IR90                                                                             IR99                                                                              IR90                                                                             IR99                              __________________________________________________________________________    COUMAPHOS   >3.9                                                                              -- >8.1                                                                              -- >1.8 --                                             COMPOSITION A                                                                             5.5 7.3                                                                              4.2 4.8                                                                              3.8  3.5                                            BROMOPHOS ETHYL                                                                           4.9 6.1                                                                              2.1 2.6                                                                              1.8  2.0                                            DIAZINON    >0.7                                                                              -- >4.5                                                                              -- >14.6                                                                              --                                             DIOXATHION  >3.9                                                                              -- >4.7                                                                              -- >5.6 --                                             CHLORPYRIFOS                                                                              4.6 6.0                                                                              2.5 3.8                                                                              3.4  7.3                                            ETHION      3.0 3.5                                                                              3.8 4.2                                                                              3.0  3.1                                            DICROTOPHOS >1.0                                                                              -- >1.6                                                                              -- >5.6 --                                             CHLORFENVINPHOS                                                                           3.1 4.1                                                                              8.1 8.1                                                                              5.7  3.0                                                                              2.8                                                                              4.6 2.0                                                                              3.8                               __________________________________________________________________________     Composition A: A 1:1, weight by weight mixture of Chlorfenvinphos and         Dioxanthion                                                                   Key: -- Ratio Ixodicide/Permethrin                                       

EXAMPLE 3 Miscible-Oil Formulations

    ______________________________________                                                    20:1 1:1      1:20                                                ______________________________________                                        Dioxathion    20.0   10.5      1.0 pts. by wt.                                Permethrin     1.0   10.5     20.0 "                                          Esso Solvent 200                                                                            59.0   54.0     49.0 "                                          Ethylan KEO   20.0   20.0     20.0 "                                          Cyclohexanone --      5.0     10.0                                                          100.0  100.0    100.0                                           ______________________________________                                    

Ethylan KEO is an emulsifying agent which is a nonyl phenol ethoxylatecondensate with an ethylene oxide average chain length of 9.5 mols,supplied by Lankro Chemicals Ltd.

Esso Solvent 200 is a mobile oil which consists of 95% of aromatichydrocarbons.

EXAMPLE 4 Dusting Powder Formulations

    ______________________________________                                                 20:1  1:1       1:20                                                 ______________________________________                                        Coumaphos  0.01    0.10      0.20  pts. by wt.                                Permethrin 0.20    0.10      0.01  "                                          Talc       99.79   99.8      99.79 "                                                     100.0   100.0     100.0                                            ______________________________________                                    

EXAMPLE 5 Wettable Powder Formulations

    ______________________________________                                                      w/w         w/w     w/w                                         ______________________________________                                        Coumaphos     1.0%        15.0%   40.0%                                       Permethrin    20.0        15.0    2.0                                         Diatomaceous Earth                                                                          76.5        50.0    --                                          Kaolin        --          17.5    54.0                                        Dispersing Agent                                                                            2.0         2.0     3.0                                         Wetting Agent 0.5         0.5     1.0                                                       100.0       100.0   100.0                                       ______________________________________                                                      w/w         w/w                                                 ______________________________________                                        Ethion        2.0         25.0                                                Permethrin    20.0        1.5                                                 Diatomaceous Earth                                                                          60.5        36.0                                                Fullers Earth 15.0        35.0                                                Dispersing Agent                                                                            2.0         2.0                                                 Wetting Agent 0.5         0.5                                                               100.0       100.0                                               ______________________________________                                    

EXAMPLE 6 Pressure-Pack Formulations

In the following examples one of three pesticide mixtures may be used:

Mixture 1

Dioxathion: 10 parts by weight

Chlorfenvinphos: 10 parts by weight

Permethrin: 1 part by weight

Mixture 2

Dioxathion: 0.5 parts by weight

Chlorfenvinphos: 0.5 parts by weight

Permethrin: 1 part by weight

Mixture 3

Dioxathion: 0.5 parts by weight

Chlorfenvinphos: 0.5 parts by weight

Permethrin: 20 parts by weight.

The above pesticide mixtures may be employed to formulate pressure packscontaining between 0.0001% w/w and 20% w/w of each pesticide mixture asillustrated by the following examples:

    ______________________________________                                        Example A                                                                     ______________________________________                                        Pesticide mixture        0.0001% w/w                                          (either No. 1, 2 or 3 above)                                                  Odourless kerosene      10.0000% w/w                                          Methyl chloroform       29.9999% w/w                                          50/50 mixture of trichlorofluoromethane                                                               60.0000% w/w                                          and dichlorodifluoromethane                                                                           100.0000% w/w                                         ______________________________________                                    

    ______________________________________                                        Example B                                                                     ______________________________________                                        Pesticide mixture   20% w/w                                                   (either No. 1, 2 or 3 above)                                                  Methyl chloroform   50% w/w                                                   Dichlorodifluoromethane                                                                           30% w/w                                                                       100% w/w                                                  ______________________________________                                    

EXAMPLE 7

Highly tick susceptible cattle were placed in tick stalls andartifically infested with 0.25 g of B. microplus (Biarra strain) larvaebefore and after treatment. Twenty-four days after introduction theanimals were divided into four groups and power-hand sprayed with 36liters of wash per animal. The washes contained the followingconcentrations of active ingredients:

Group 1: 500 ppm Ethion

Group 2: 100 ppm permethrin

Group 3: 100 ppm permethrin and 500 ppm Ethion

Group 4: 50 ppm permethrin and 500 ppm Ethion.

Engorged female ticks were collected daily from the washing baskets andcounted. The results are illustrated in Table 5.

EXAMPLE 8

Engorged female ticks of the Biarra strain of B. microplus were immersedin serial ranges of concentrations of certain ixodicides alone. Theticks were then dried and stuck, dorsal side down, on double-sidedsellotape. After 14 days the numbers of ticks laying viable egg batcheswere determined and the percentage plotted against concentration and aregression line drawn. The IR90/99 values were then determined as inExample 1. Having thus established the IR90/99 values for each of thechemicals under test equitoxic mixtures each comprising permethrin withone of the other ixodicides were prepared at the ratio of the IR99values obtained. The master solutions were then diluted with water tothe required range for the immersion test.

The results are illustrated in Table 10.

                                      TABLE 6                                     __________________________________________________________________________    LC50 values of individual organophosphorus                                    insecticides and compositions of these with                                   permethrin obtained both theoretically and                                    by experiment against Musca domestica                                         (CTB strain) (ratio 1:1)                                                               Experimental   Calculated                                                            LC50 Mixture   LC50 Mixture                                            LC50 Alone                                                                           as permethrin                                                                         LC50 Total                                                                           as permethrin                                                                         Factor of                              Compound (μg/♀)                                                                     (μg/♀)                                                                      (μg/♀)                                                                     (μg/♀)                                                                      Potentiation                           __________________________________________________________________________    Permethrin                                                                             0.027  --      --     --      --                                     Bromophos ethyl                                                                        0.102  0.029   0.043  0.021   0.74                                   Chlorpyrifos                                                                           0.094  0.025   0.042  0.021   0.84                                   Bromophos                                                                              0.114  0.021   0.043  0.022   1.02                                   Malathion                                                                              1.349  0.036   0.053  0.026   0.73                                   Diazinon 0.041  0.025   0.032  0.016   0.66                                   __________________________________________________________________________     LC50 is the minimum lethal dose expressed in μg required to kill 50% o     the flies                                                                

                                      TABLE 7                                     __________________________________________________________________________    LC95 values of individual organophosphorus                                    insecticides and compositions of these with                                   permethrin obtained both theoretically and                                    by experiment against Musca domestica                                         (CTB strain) (ratio 1:1)                                                               Experimental   Calculated                                                            LC95 Mixture   LC95 Mixture                                            LC95 Alone                                                                           as permethrin                                                                         LC95 Total                                                                           as permethrin                                                                         Factor of                              Compound (μg/♀)                                                                     (μg/♀)                                                                      (μg/♀)                                                                     (μg/♀)                                                                      Potentiation                           __________________________________________________________________________    Permethrin                                                                             0.054  --      --     --      --                                     Bromophos ethyl                                                                        0.170  0.097   0.082  0.041   0.43                                   Chlorpyrifos                                                                           0.161  0.083   0.081  0.041   0.49                                   Bromophos                                                                              0.241  0.063   0.088  0.044   0.70                                   Malathion                                                                              3.671  0.105   0.107  0.053   0.51                                   Diazinon 0.160  0.066   0.081  0.040   0.61                                   __________________________________________________________________________     LC95 is the minimum lethal dose expressed in μg required to kill 95% o     the flies                                                                

                                      TABLE 8                                     __________________________________________________________________________    LD50 values for individual organophosphorus                                   insecticides and compositions of these with                                   permethrin at various ratios against Musca                                    domestica (Piggery II strain)                                                             Ratio 1:1        Ratio 1:10 (permethrin/OP)                                                                     Ratio 1:25 (permethrin/OP)              LD50           Calculated       Calculated       Calculated           Compound                                                                              (μ/♀)                                                                   Calculated                                                                          observed                                                                           observed                                                                            Calculated                                                                          observed                                                                           observed                                                                            Calculated                                                                          observed                                                                           observed             __________________________________________________________________________    Permethrin                                                                            0.235                                                                             --    --   --    --    --   --    --    --   --                   Dimethoate                                                                            0.179                                                                             0.20  0.20 1.0   0.18  0.13 1.4   --    --   --                   Diazinon                                                                              2.075                                                                             0.41  0.35 1.2   1.2   0.89 1.4   --    --   --                   Malathion                                                                             41.70                                                                             0.46  0.42 1.1   2.45  2.49 1.0   5.36  3.0  1.8                  Chlorpyrifos                                                                          2.171                                                                             0.41  0.38 1.1   1.25  0.76 1.7   --    --   --                   Bromophos                                                                             2.663                                                                             0.42  0.39 1.1   1.38  0.50 2.8   --    --   --                   ethyl                                                                         Pirimiphos                                                                            5.130                                                                             0.44  0.38 1.2   1.78  1.22 1.5   2.85  1.77 1.6                  methyl                                                                        __________________________________________________________________________     LD50 is the minimum lethal dose expressed in μg required to kill 50% o     the flies                                                                     OP = organophosphorus compound                                                ##STR3##                                                                 

                                      TABLE 9                                     __________________________________________________________________________    LD95 values for individual organophosphorus                                   insecticides and compositions of these with                                   permethrin at various ratios against Musca                                    domestica (Piggery II strain)                                                             Ratio 1:1        Ratio 1:10 (permethrin/OP)                                                                     Ratio 1:25 (permethrin/OP)              LD95           Calculated       Calculated       Calculated           Compound                                                                              (μg/♀)                                                                  Calculated                                                                          observed                                                                           observed                                                                            Calculated                                                                          observed                                                                           observed                                                                            Calculated                                                                          observed                                                                           observed             __________________________________________________________________________    Permethrin                                                                            0.63                                                                              --    --   --    --    --   --    --    --   --                   Dimethoate                                                                            0.66                                                                              0.65  0.53 1.2   0.66  0.62 1.1   --    --   --                   Diazinon                                                                              5.12                                                                              1.16  1.06 1.1   3.11  2.84 1.1   --    --   --                   Malathion                                                                             177.5                                                                             1.30  1.03 1.3   6.70  9.00 0.7   15.05 8.00 1.9                  Chlorpyrifos                                                                          10.66                                                                             1.23  0.85 1.5   4.36  1.79 2.4   --    --   --                   Bromophos                                                                             11.62                                                                             1.24  0.91 1.4   4.50  1.82 2.5   --    --   --                   ethyl                                                                         Pirimiphos                                                                            15.6                                                                              1.26  0.91 1.4   4.92  3.28 1.5    8.15 5.02 1.6                  methyl                                                                        __________________________________________________________________________     LD95 is the minimum lethal dose expressed in μg required to kill 95% o     the flies                                                                     OP = organophosphorus compound                                                ##STR4##                                                                 

                                      TABLE 10                                    __________________________________________________________________________    The activity of equitoxic mixtures of certain organo-                         phosphorus ixodicides with permethrin against viable                          oviposition of engorged female ticks of the Biarra                            strain of B. microplus                                                                        EQUITOXIC MIXTURE                                             Permethrin                                                                             ALONE  Expected Value                                                                        Actual Value                                                                         Factor of Potentiation                         Composite with                                                                         IR90                                                                              IR99                                                                             IR90                                                                              IR99                                                                              IR90                                                                             IR99                                                                              IR90 IR99                                      __________________________________________________________________________    Ethion   0.14                                                                              0.23                                                                             0.10                                                                              0.18                                                                              0.012                                                                            0.024                                                                             8.3  7.5                                       Chlorfenvinphos                                                                        0.15                                                                              0.42                                                                             0.11                                                                              0.28                                                                              0.025                                                                            0.059                                                                             4.4  4.7                                       Permethrin                                                                              0.066                                                                            0.13                                                             __________________________________________________________________________     ##STR5##                                                                      IR90 = concentration at which 90% inhibition of egg laying occurs             IR99 = concentration at which 99% inhibition of egg laying occurs        

EXAMPLE 9

    ______________________________________                                        Aqueous Suspension Formulations                                                                % w/w                                                                         (a)   (b)      (c)                                           ______________________________________                                        Permethrin         1.0     8.0      20.0                                      Coumaphos          20.0    8.0      1.0                                       Sodium Dioctyl Sulphosuccinate                                                                   0.2     0.2      0.2                                       Xanthan Gum        0.3     0.4      0.3                                       Water              78.5    83.4     78.5                                                         100.0   100.0    100.0                                     ______________________________________                                    

EXAMPLE 10

    ______________________________________                                        Diluent Free Formulations                                                                % w/w                                                                         (a)       (b)     (c)                                              ______________________________________                                        Permethrin   3.5         38.0    72.0                                         Diazinon     70.0        38.0    3.6                                          Epichlorhydrin                                                                             7.0         4.0     0.4                                          Ethylan KEO  19.5        20.0    24.0                                                      100.0       100.0   100.0                                        ______________________________________                                    

Ethylan KEO is an emulsifying agent which is a nonyl phenol ethoxylatecondensate with an ethylene oxide average chain length of 9.5 mols,supplied by Lankro Chemicals Ltd.

REFERENCE EXAMPLE A

Mixtures of permethrin in combination with various organophosphoruscompounds were prepared at 1:1, 1:10 and 1:25 ratios (ratio permethrinto organophosphorus compound). Solutions of the pesticides alone weresimilarly prepared.

The individual pesticides and the mixtures were diluted appropriatelyand applied by means of a microsyringe to the dorsal thorax of femaleCTB or Piggery II strain Musca domestica flies. This topical applicationtechnique was performed on twenty females flies for each concentrationof each mixture. The flies were then placed in a cardboard carton withaccess to sugar water for one day in order to assess mortality. Eachconcentration of each mixture was tested five times in a linked sequenceover a period of several weeks.

The LC50 and LC95 value of each mixture was determined by means ofprobit analysis. A theoretical LC50 and LC95 value was calculated foreach mixture by means of the equation of the harmonic mean.

The theoretical and experimental values were then compared in order togive factors of potentiation values.

The results are given in Tables 6 to 9, which indicate that little or nopotentiation was observed.

What we claim is:
 1. An acaricidal composition comprising an amount of afirst pyrethroid compound permetherin and a second compound diazinon,the first and second compounds being present in an amount to provide asynergistic combination.
 2. A method of controlling veterinaryectoparasites of mammals and birds of the sub-orders Ixodoidea andSarcoptiformes, which comprises the application of a parasiticidallyeffective amount, which is non-toxic to mammals or birds of thecomposition of claim 1.